The objective of our studies has been the further characterization of Rathke's pouch (RP)-derived tissues, and the elucidation of those factors that may influence its growth and development either in normal or tumorous directions. Our continuing studies will further test the tumor susceptibility of 12-day RP transplanted beneath the kidney capsule (KC) and stimulated by exogenous estradiol, and also the possible influence on development of tissues associated with the microsurgically isolated RP, e.g., RP-mesenchyme and adjacent ventral hypothalamus. Studies of implantation of RP to brain sites will be particularly concerned with the importance of the exact site of implantation into the median eminence region on graft development. Parallel in vitro studies also will be testing the possible influences on RP development of adult median eminence extract, embryonic brain extract, luteinizing hormone-releasing hormone, thyrotropin hormone-releasing hormone, and estrogen. Tissues will be studied by light and electron microscopy, immunohistochemistry, and the secretion of hormones will be assayed by radioimmunoassay.